Re: git: 9b967bd65de6 - main - domains: allow domains to be unloaded

> On 14 Aug 2022, at 15:51, Kyle Evans <kevans@FreeBSD.org> wrote:
> 
> On Sun, Aug 14, 2022 at 2:22 AM Alexander V. Chernikov
> <melifaro@freebsd.org> wrote:
>> 
>> The branch main has been updated by melifaro:
>> 
>> URL: https://cgit.FreeBSD.org/src/commit/?id=9b967bd65de6647aed68a141dc34f9b223a2593c
>> 
>> commit 9b967bd65de6647aed68a141dc34f9b223a2593c
>> Author:     Alexander V. Chernikov <melifaro@FreeBSD.org>
>> AuthorDate: 2022-08-12 13:36:53 +0000
>> Commit:     Alexander V. Chernikov <melifaro@FreeBSD.org>
>> CommitDate: 2022-08-14 09:22:33 +0000
>> 
>>    domains: allow domains to be unloaded
>> 
>>    Add domain_remove() SYSUNINT callback that removes the domain
>>     from the domain list if it has DOMF_UNLOADABLE flag set.
>>    This change is required to support netlink ( D36002 ).
>> 
>>    Reviewed by:    glebius
>>    Differential Revision: https://reviews.freebsd.org/D36173
>> ---
>> sys/kern/uipc_domain.c | 23 +++++++++++++++++++++++
>> sys/sys/domain.h       |  4 ++++
>> 2 files changed, 27 insertions(+)
>> 
>> diff --git a/sys/kern/uipc_domain.c b/sys/kern/uipc_domain.c
>> index c70b3150cbf0..2cae08be089a 100644
>> --- a/sys/kern/uipc_domain.c
>> +++ b/sys/kern/uipc_domain.c
>> @@ -239,6 +239,29 @@ domain_add(void *data)
>>        mtx_unlock(&dom_mtx);
>> }
>> 
>> +void
>> +domain_remove(void *data)
>> +{
>> +       struct domain *dp = (struct domain *)data;
>> +
>> +       if ((dp->dom_flags & DOMF_UNLOADABLE) == 0)
>> +               return;
>> +
>> +       mtx_lock(&dom_mtx);
>> +       if (domains == dp) {
>> +               domains = dp->dom_next;
>> +       } else {
>> +               struct domain *curr;
>> +               for (curr = domains; curr != NULL; curr = curr->dom_next) {
>> +                       if (curr->dom_next == dp) {
>> +                               curr->dom_next = dp->dom_next;
>> +                               break;
>> +                       }
>> +               }
>> +       }
>> +       mtx_unlock(&dom_mtx);
>> +}
>> +
>> /* ARGSUSED*/
>> static void
>> domaininit(void *dummy)
> 
> While it's not important for the one domain you care about, this
> should likely also check if any contained protocols have
> pr_fasttimo/pr_slowtimo and purge them from the appropriate list, just
> to be technically correct. (Or at least assert under INVARIANTS that
> they do not)
That’s a good point!
I should have provided more context in the commit message.
There is some ongoing work glebius@ is doing in the domain space.
Specifically, there are plans to remove this callbacks in the near future - https://reviews.freebsd.org/D36163 stack provides more reasoning and implementation details.
Additionally, the KPI may be a bit fluid and may change in the near/mid-term future - that’s why the minimal working version was committed.